1. Field
The present document relates to a travel route stray discriminating method of a mobile object in a navigation system configured to discriminate whether a mobile object has diverted from a searched travel route to travel on a different travel route.
2. Description of the Related Art
Concomitant with the continuous increase of the number of mobile objects such as vehicles, traffic congestion is getting worsened these days. Particularly, traffic problems are aggravated as the increase of the number of mobile objects is faster than that of the expansion of infrastructures of roads and bridges.
One of the solutions worth noticing for addressing the traffic congestion is a navigation system.
Generally, a navigation system is such that at least four or more navigation messages are received by a Global Positioning System (GPS) receiver out of navigation messages periodically transmitted by a plurality of GPS satellites arranged on geostationary orbits over the Earth to detect 3D location coordinates of a mobile object. The location coordinates detected by the GPS receiver are determined as a current location of a mobile object, and the detected current location of the mobile object is map-matched on a digital map so that the digital map and the location of the mobile object can be displayed on a display screen.
Furthermore, the navigation system searches a travel route from a current location of a mobile object to a destination, and guides a user to steer a mobile object along the searched travel route. Therefore, if the navigation system is used, there is an advantage in that a travel route of a mobile object can be searched and guided to allow using a given road network effectively.
If there is positioned a cross section in front of a traveling mobile object, or there is located a guidance subject matter such as a highway, or a leading route to an interchange of a highway or a freeway, the navigation system searches for those subject matters.
If a mobile object approaches within a predetermined distance of the searched guidance subject matter, the navigation system guides via a voice signal a travel route of the mobile object at a location of the guidance subject matter. Furthermore, the navigation system discriminates whether the mobile object has diverted from the searched travel route to other travel routes, and if the travel routed has been diverted, the navigation system informs a user of the diversion of the travel route and enables the mobile object to travel on an accurate travel route.
FIGS. 1a and 1b are signal flow charts illustrating an operation of a navigation system of a mobile object whether a mobile object has diverted from a searched travel route.
First of all, a user of a navigation system inputs a starting point and a destination of a mobile object (S100), and instructs the navigation system to search a travel route (S102). The navigation system then searches the start point to the destination on the travel route and displays the searched travel route on a display screen to allow the user to check the searched travel route (S104).
If the mobile object travels (S106), the navigation system discriminates a current location of the mobile object by using a navigational method in which navigational messages received by GPS receiver and a travel status detection signal of the mobile object detected by a sensor mounted at the mobile object are mixed (S108). The navigation system then discriminates whether the current location of the mobile object thus discriminated at S108 is a destination (S110).
As a result of the discrimination if the current location of the mobile object is the destination, the navigation system completes a guidance operation of the travel route (S112). If the current location is not the destination as a result of the discrimination, the navigation system discriminates whether the current location of the mobile object is on the searched travel route (S114).
As a result of discrimination at S114, if the current location of the mobile object is not situated on the searched travel route, and is diverted therefrom, the navigation system calculates a diverted straight distance between the current location of the diverted mobile object and the travel route (S118). If the strayed straight distance is calculated, the navigation system discriminates whether the calculated diverted straight distance exceeds a predetermined set threshold distance (S120).
As a result of the discrimination, if the diverted straight distance is less than the threshold, the navigation system discriminates that the mobile object has not strayed from the travel route, and flow returns to S108, and the navigation system searches for the current location of the mobile object and repeats the operations of discriminating whether the mobile object has arrived at the destination and strayed from the travel route.
As a result of the discrimination at S120, if the diverted straight distance exceeds the threshold distance, the navigation system discriminates that the mobile object has strayed from the travel route, and outputs a voice signal and guides the diversion of the travel route (S122). Furthermore, the navigation system re-searches for the travel route of the mobile object from the diverted location and repeats the operations of discriminating whether the mobile object has arrived at the destination and strayed from the travel route.
The technique thus described according to the prior art uses only the straight distance diverted from the travel route to discriminate whether the mobile object has strayed from the travel route. Consequently, even if the mobile object travels along a travel route at a congested area such as a crossroad and the like, the navigation system discriminates that the mobile object has strayed from the travel route, and generates an error of issuing a warning that the mobile object has strayed from the travel route. As a result, the navigation system has caused an inconvenience to the user's safe driving.
Still worse, if a mobile object strays from a given travel route to travel a road within a threshold distance, for example, if the mobile object travels on a road in parallel with the travel route and within the threshold distance, the navigation system generates an error of not discriminating that the mobile object has strayed from the travel route.